This invention pertains to improvements in tire valves, and more particularly, to a novel construction for the insides or valve core therefor.
It has been recognized as highly desirable in the manufacture of tire valves and the like that the insides of the valve, or what is commonly termed the valve core, be inexpensively reproducible. Also, it is very advantageous if the core is adapted to fit a standard drilled valve body.
The fabrication of conventional tire valve cores of metal has involved the requirement that the barrel or core body be of reasonably thin construction such that the cost of manufacture of such an article will not be prohibitive. This has commonly led to the formation of a valve core structure with a dynamic sealing arrangement that provides a cup-like member at the end of the core pin. For an example of such a configuration or structure, reference may be made to U.S. Pat. No. 4,091,999. In accordance with that construction, a disc shaped rubber sealing means is fitted within the cup-like member and is normally pressed against the end of the metallic barrel of the valve core with sufficient force to provide an air-tight seal. Reference may also be made to U.S. Pat. No. 1,991,974 in which a springless construction for a tire valve core is disclosed.
Because of the limitation on the thickness of the metallic barrel dictated by cost considerations, the rubber sealing means or washer associated therewith makes surface contact over a rather limited area with respect to the end of the barrel. Also, such construction has the disadvantage that should any minute particles of dirt be lodged in the cup-like member, that is, in contact with the washer or grommet, a sufficiently tight seal will not be produced. Moreover, it is often found in practice that at high speeds the inertia of the movable parts of the valve core may break the seal; thus, for example, when the tire travels over a rough road or is subject to severe jolting, air may be allowed to escape, this being more so in the case of a valve core construction which involves the aforesaid cup-like closure member.
Accordingly, it has been a long sought after objective to eliminate some of the disadvantageous aspects of metallic valve core construction. To this end certain proposals of plastic valve cores, or at least of the barrels thereof, have been disclosed in the prior art. In order to furnish background for the present invention in this connection reference may be made to U.S. Pat. No. 3,207,172 in which a molded nylon cylindrical barrel for a valve core is disclosed, such barrel having an axial bore extending through and, in particular, having an outwardly tapered bearing surface at the lower or second end of the barrel. One of the objects of the invention in such patent is to advantageously exploit the capability of the material, that is, the plastic of which the barrel is composed, to provide a static seal with respect to the standard core drilling taper seat. In other words, the unit is self-sealing because the polymeric or plastic material itself provides the static seal with respect to the valve body.
However advantageous and beneficial the different aspects of the prior art proposals and particularly of the valve core proposed or disclosed in 3,207,172, the fact remains that in most instances it is preferable to have a greater surface area than there afforded for the purpose of effectuating a safe seal. Moreover, with respect to the aforementioned sealing of a metallic barrel according to which a cup-like member is employed, the structure of that cup-like member is such that it tends to cause on occasion a hanging up of the valve sealing means. This can be understood inasmuch as the internal bore of the valve stem or body into which the valve core is fitted, is narrowly dimensioned and sufficient clearance is not always attained.
It is therefore a primary object of the present invention to provide a valve core that will result in substantial reduction in material costs and in cost of manufacture and assembly of components, while insuring that a sufficiently broad annular surface area will be provided at the end of the valve core barrel so that an efficient and safe sealing will be achieved.
A further object is to provide a valve core that will fit into a standard drilled valve body, and yet will be self-sealing into the standard tapered seat therein.
Another object of the present invention is to hold the various components of the valve core to close dimensional tolerances, that is to say, to closer tolerances than formerly provided by pressed or formed parts conventionally used. This is accomplished because of the nature of the material, that is, because a plastic is involved and injection molding techniques may be utilized.
Yet another fundamental object of the present invention is to provide flexibility in the fabrication of a valve core such that an external closing spring can be incorporated into the construction but need not be. Thus the spring is incorporated only so as to meet specific service requirements.
Briefly, the present invention comprises a molded or otherwise formed plastic, e.g., polymeric, valve core including a cylindrical barrel having an axial bore extending therethrough, and having an external threaded portion thereon near a first or outer end of said barrel for threadable engagement with the interior threads of a valve stem or body. The second or inner part of the barrel is adapted by itself to provide the requisite static seal with respect to said valve body. The second end of the barrel has a substantial annular thickness of the order of 0.035-0.040 inches. This broad annulus constitutes the seating means for the valve proper, and a suitable sealing gasket or washer is adapted to be compressed against the seat provided by the annular end. This sealing washer fits around the end of the pin of the valve core, it being understood that the valve core of the present invention comprises the three simple components only, namely, the already described valve barrel, the pin member, and the sealing washer. The pin member is provided with a conical or tapered portion, near its second end, and includes a cylindrical portion just beyond that conical portion, which is surrounded by the sealing washer. The sealing washer has its lower surface abutting the enlarged cylindrical end portion of the pin. Moreover, the sealing washer has an outside diameter which substantially corresponds with the outside diameter of that end portion of the valve pin. Consequently, the aforedescribed required efficient sealing is attained, while there is avoided the possibility of the hang-up presented by an element such as the cup-like member of a conventional metallic valve core.
A substantial advantage of the construction of a valve core in accordance with the invention is that a recess does not have to be made in the valve body as is done in accordance with conventional practice. The reason for this practice is that due to the size and shape of a valve core that is to be fitted into a conventionally drilled standard valve body, the recess is necessary to allow for properly inflating a device such as a tire or the like. However, in the present instance the configuration is such that the charging of air when inflating is in a straight down manner and as a result the recess does not have to be provided. Consequently, a stronger valve is achievable than those obtained by following conventional practice.
Other and further objects, advantages and features of the present invention will be understood by reference to the following specification in conjunction with the annexed drawing, wherein like parts have been given like numbers.